[wip] pointer decompression no-op [v8/v8 : main]

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Steinar H Gunderson (Gerrit)

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Dec 19, 2025, 4:29:03 AM (10 days ago) Dec 19

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[wip] pointer decompression no-op

Change-Id: I1480f0032e3733972553b1e34eb4a7def5f157ed

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diff --git a/include/cppgc/internal/member-storage.h b/include/cppgc/internal/member-storage.h
index f862740..7fff2ea 100644
--- a/include/cppgc/internal/member-storage.h
+++ b/include/cppgc/internal/member-storage.h
@@ -154,6 +154,14 @@
     // the cage alignment.
     CPPGC_DCHECK((!compressed || compressed == kCompressedSentinel) ||
                  (compressed & (1 << 31)));
+
+    // Tell the compiler that decompressing this compressed pointer
+    // is a no-op. Note that Clang is unable to inline Decompress()
+    // into an assume, so we need to write it out fully.
+    [[assume(((static_cast<uint64_t>(static_cast<int32_t>(compressed))
+               << api_constants::kPointerCompressionShift) &
+              base) == uptr)]];
+
     return compressed;
   }

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M include/cppgc/internal/member-storage.h

Change size: XS

Delta: 1 file changed, 8 insertions(+), 0 deletions(-)

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Dec 19, 2025, 5:27:02 AM (10 days ago) Dec 19

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